Internal combustion engine



FIG. 1 is a front, left side perspective view of an internal combustion engine according to our new design;

FIG. 2 is a front, right side perspective view thereof;

FIG. 3 is a rear, left side perspective view thereof;

FIG. 4 is a rear, right side perspective view thereof;

FIG. 5 is a front elevational view thereof;

FIG. 6 is a left side elevational view thereof;

FIG. 7 is a top view thereof;

FIG. 8 is a right side elevational view thereof;

FIG. 9 is a rear elevational view thereof; and,

FIG. 10 is a bottom view thereof.

The broken lines in the figures are for illustrative purposes only and form no part of the claimed design. 

The ornamental design for an internal combustion engine, as shown and described. 